When stretch marks occur

if you have an underlying health condition or a syndrome, such as Cushing's syndrome or Marfan syndrome

after the prolonged or inappropriate use of corticosteroid medication

These are discussed in more detail below.

Pregnancy

Stretch marks often occur during the later stages of pregnancy, affecting about 8 out of 10 pregnant women. Whether or not you'll get stretch marks depends on your skin type and how elastic it is.

During pregnancy, hormones are produced that soften the ligaments in your pelvis so they're more flexible when you give birth. Ligaments are strong bands of tissue that connect joints. However, the hormones also soften the fibres in your skin, making it prone to stretch marks.

As your baby grows and your skin stretches, you may get stretch marks on your tummy. You may also develop them on your thighs and breasts as they get bigger.

Stretch marks usually fade and become less noticeable after childbirth, but they don't always disappear completely.

Rapid weight gain

You may get stretch marks if you put on a lot of weight over a short period of time. They sometimes remain even after losing weight, but should eventually fade.

Regular dieting can cause stretch marks as your weight goes up and down. If you need to lose weight, lose it slowly and steadily so that your skin isn't put under strain. Read more about how to lose weight safely.

Bodybuilders and athletes can also get stretch marks as their muscles increase in size.

Puberty

During puberty, the body often develops very quickly in growth spurts.

Boys may get stretch marks on their shoulders and back, and girls may get them on their hips, thighs and breasts.

Family history

If you have a close relative with stretch marks, such as your mother, you're more likely to develop them yourself.

Although stretch marks can affect both male and female family members, they're more common in women.

Underlying health conditions

Cushing's syndrome occurs when the body overproduces the hormone cortisol, which is thought to cause stretch marks.

Marfan syndrome is caused by a faulty gene that weakens the body's skin and connective tissues, reducing their elasticity (ability to stretch). This means the skin isn't as resistant to stretch marks as it should be.

In Marfan syndrome, stretch marks can occur on the shoulders, hips and lower back.

Corticosteroids

In rare cases, stretch marks can develop after prolonged or inappropriate use of corticosteroids, such as creams or lotions used to treat skin conditions, including eczema.

Corticosteroids work in a similar way to the hormone cortisol. They can help ease inflammatory skin conditions but, like cortisol, they can also reduce the amount of collagen in your skin.

Collagen is a protein that helps keep your skin stretchy. The less collagen there is in your skin, the more likely you are to develop stretch marks.

When using a corticosteroid cream or lotion, follow the manufacturer's instructions about how and where to apply it. The face, groin and armpits are particularly sensitive areas. Ask your GP or pharmacist for advice if you're unsure.

How stretch marks develop

Before stretch marks appear, the affected skin will become thin, flattened and pink, and may feel itchy.

The stretch marks themselves appear as red or purple streaks or lines, but can be pink, reddish-brown or dark brown, depending on your skin colour.

They can occur in patches of parallel lines on your body and often appear "scar-like". To start with, the lines will be slightly raised and may feel wrinkly, before eventually flattening out.

As the lines become flatter, they'll start to fade and change to a white or silvery colour. They'll usually become less noticeable over time, although this process can sometimes take years.

What causes stretch marks?

Stretch marks are caused when the skin rapidly stretches as a result of sudden growth or weight gain.

The stretching causes the middle layer of skin (dermis) to tear, allowing the deeper skin layers to show through, forming stretch marks.

The dermis contains strong, inter-connected fibres that allow your skin to stretch as your body grows. However, rapid growth can cause the skin to over-stretch and break the fibres.

The tears in the dermis allow the blood vessels below to show through, which is why stretch marks are often red or purple when they first appear.

When the blood vessels eventually contract (get smaller), the pale-coloured fat underneath your skin will be visible, and your stretch marks will change to a silvery-white colour.

Treating stretch marks

Most stretch marks aren't particularly noticeable and will fade over time.

If you have unsightly stretch marks, or if they affect a large area of your body, there are a few treatment options available. However, there isn't much evidence to show that these treatments work.

Camouflage

Cosmetic camouflage (make-up) is available over-the-counter at pharmacies. It can be used for small areas of skin affected by stretch marks. Some types are waterproof and can last two to three days.

Creams, gels and lotions

The manufacturers of creams, gels and lotions often claim that they can remove stretch marks. However, it's unlikely they can prevent stretch marks occurring, or make them fade any more than they will over time.

These products are essentially skin moisturisers and are available from pharmacies, supermarkets, and health and beauty shops. They should usually be applied when your stretch marks are still red or purple.

Laser therapy

Laser therapy can't completely remove stretch marks, but it may help fade them and make them less noticeable.

Several different types of laser therapy are used to treat stretch marks.

Pulsed dye laser treatment is one type of laser treatment available. It's painless and can be used at an early stage, while your stretch marks are still red or purple.

The energy from the laser is absorbed by the blood vessels underneath your stretch marks. The blood vessels collapse and the red or purple colour either disappears completely or turns white.

Laser therapy for stretch marks isn't available on the NHS and it's usually expensive. You'll probably need a few treatments to obtain visible results. The exact number will depend on your skin colour and type.

It's important to eat a healthy, balanced diet that's rich in vitamins and minerals, particularly vitamin E, vitamin C, and the minerals zinc and silicon. These vitamins and minerals will help keep your skin healthy.

During pregnancy

Stretch marks during pregnancy (striae gravidarum) are usually caused by hormonal changes that affect your skin. Gaining pregnancy weight steadily may help minimise the effect of stretch marks.

During pregnancy, it's normal to put on weight over a relatively short period of time. However, it's a myth that you need to "eat for two", even if you're expecting twins or triplets.

If you're pregnant you don't need to go on a special diet, but you should eat a variety of foods every day to get the right balance of nutrients for you and your baby. Your diet should be rich in wholewheat carbohydrates, such as bread and pasta, as well as fruit and vegetables.